/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 * <p>
 * http://www.apache.org/licenses/LICENSE-2.0
 * <p>
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.hadoop.hdfs.server.datanode;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.security.PrivilegedExceptionAction;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;

import org.apache.commons.logging.Log;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hdfs.DFSConfigKeys;
import org.apache.hadoop.hdfs.DFSUtil;
import org.apache.hadoop.security.UserGroupInformation;

import com.google.common.base.Joiner;
import com.google.common.base.Preconditions;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;
import com.google.common.collect.Sets;

/**
 * Manages the BPOfferService objects for the data node.
 * Creation, removal, starting, stopping, shutdown on BPOfferService
 * objects must be done via APIs in this class.
 */
@InterfaceAudience.Private
class BlockPoolManager {
    private static final Log LOG = DataNode.LOG;

    private final Map<String, BPOfferService> bpByNameserviceId =
            Maps.newHashMap();
    private final Map<String, BPOfferService> bpByBlockPoolId =
            Maps.newHashMap();
    private final List<BPOfferService> offerServices =
            Lists.newArrayList();

    private final DataNode dn;

    //This lock is used only to ensure exclusion of refreshNamenodes
    private final Object refreshNamenodesLock = new Object();

    BlockPoolManager(DataNode dn) {
        this.dn = dn;
    }

    synchronized void addBlockPool(BPOfferService bpos) {
        Preconditions.checkArgument(offerServices.contains(bpos),
                "Unknown BPOS: %s", bpos);
        if (bpos.getBlockPoolId() == null) {
            throw new IllegalArgumentException("Null blockpool id");
        }
        bpByBlockPoolId.put(bpos.getBlockPoolId(), bpos);
    }

    /**
     * Returns the array of BPOfferService objects.
     * Caution: The BPOfferService returned could be shutdown any time.
     */
    synchronized BPOfferService[] getAllNamenodeThreads() {
        BPOfferService[] bposArray = new BPOfferService[offerServices.size()];
        return offerServices.toArray(bposArray);
    }

    synchronized BPOfferService get(String bpid) {
        return bpByBlockPoolId.get(bpid);
    }

    synchronized void remove(BPOfferService t) {
        offerServices.remove(t);
        if (t.hasBlockPoolId()) {
            // It's possible that the block pool never successfully registered
            // with any NN, so it was never added it to this map
            bpByBlockPoolId.remove(t.getBlockPoolId());
        }

        boolean removed = false;
        for (Iterator<BPOfferService> it = bpByNameserviceId.values().iterator();
             it.hasNext() && !removed; ) {
            BPOfferService bpos = it.next();
            if (bpos == t) {
                it.remove();
                LOG.info("Removed " + bpos);
                removed = true;
            }
        }

        if (!removed) {
            LOG.warn("Couldn't remove BPOS " + t + " from bpByNameserviceId map");
        }
    }

    void shutDownAll(BPOfferService[] bposArray) throws InterruptedException {
        if (bposArray != null) {
            for (BPOfferService bpos : bposArray) {
                bpos.stop(); //interrupts the threads
            }
            //now join
            for (BPOfferService bpos : bposArray) {
                bpos.join();
            }
        }
    }

    synchronized void startAll() throws IOException {
        try {
            // 这块东西隐藏了极为关键的逻辑,这里包含了最核心的东西,datanode启动的时候,要向namenode去进行注册
            // 让namenode感知到自己
            UserGroupInformation.getLoginUser().doAs(
                    new PrivilegedExceptionAction<Object>() {
                        @Override
                        public Object run() throws Exception {
                            // 启动BPserviceActor线程
                            for (BPOfferService bpos : offerServices) {
                                bpos.start();
                            }
                            return null;
                        }
                    });
        } catch (InterruptedException ex) {
            IOException ioe = new IOException();
            ioe.initCause(ex.getCause());
            throw ioe;
        }
    }

    void joinAll() {
        for (BPOfferService bpos : this.getAllNamenodeThreads()) {
            bpos.join();
        }
    }

    void refreshNamenodes(Configuration conf)
            throws IOException {
        LOG.info("Refresh request received for nameservices: " + conf.get
                (DFSConfigKeys.DFS_NAMESERVICES));

        Map<String, Map<String, InetSocketAddress>> newAddressMap = DFSUtil
                .getNNServiceRpcAddressesForCluster(conf);

        synchronized (refreshNamenodesLock) {
            doRefreshNamenodes(newAddressMap);
        }
    }

    private void doRefreshNamenodes(
            Map<String, Map<String, InetSocketAddress>> addrMap) throws IOException {
        assert Thread.holdsLock(refreshNamenodesLock);

        Set<String> toRefresh = Sets.newLinkedHashSet();
        Set<String> toAdd = Sets.newLinkedHashSet();
        Set<String> toRemove;

        synchronized (this) {
            // Step 1. For each of the new nameservices, figure out whether
            // it's an update of the set of NNs for an existing NS,
            // or an entirely new nameservice.
            for (String nameserviceId : addrMap.keySet()) {
                if (bpByNameserviceId.containsKey(nameserviceId)) {
                    toRefresh.add(nameserviceId);
                } else {
                    toAdd.add(nameserviceId);
                }
            }

            // Step 2. Any nameservices we currently have but are no longer present
            // need to be removed.
            toRemove = Sets.newHashSet(Sets.difference(
                    bpByNameserviceId.keySet(), addrMap.keySet()));

            assert toRefresh.size() + toAdd.size() ==
                    addrMap.size() :
                    "toAdd: " + Joiner.on(",").useForNull("<default>").join(toAdd) +
                            "  toRemove: " + Joiner.on(",").useForNull("<default>").join(toRemove) +
                            "  toRefresh: " + Joiner.on(",").useForNull("<default>").join(toRefresh);


            // Step 3. Start new nameservices
            if (!toAdd.isEmpty()) {
                LOG.info("Starting BPOfferServices for nameservices: " +
                        Joiner.on(",").useForNull("<default>").join(toAdd));

                // 这个BPOfferService,BPServiceActor
                // nameservice,一组namenode,两个namenode组成的,就是一个Active+一个standby
                // 一组namenode就是一个nameservice
                // 对每个nameservice(一组namenode),就去创建一个BPOfferService
                // 如果你仅仅用的是hadoop的普通的HA架构,就只有一个nameservice,也就只有一个nameservice
                for (String nsToAdd : toAdd) {
                    ArrayList<InetSocketAddress> addrs =
                            Lists.newArrayList(addrMap.get(nsToAdd).values());
                    BPOfferService bpos = createBPOS(addrs);
                    bpByNameserviceId.put(nsToAdd, bpos);
                    offerServices.add(bpos);
                }
            }
            startAll();
        }

        // Step 4. Shut down old nameservices. This happens outside
        // of the synchronized(this) lock since they need to call
        // back to .remove() from another thread
        if (!toRemove.isEmpty()) {
            LOG.info("Stopping BPOfferServices for nameservices: " +
                    Joiner.on(",").useForNull("<default>").join(toRemove));

            //如果有一些nameservice要删除,那么就要停止他对应的BPServiceActor线程
            for (String nsToRemove : toRemove) {
                BPOfferService bpos = bpByNameserviceId.get(nsToRemove);
                bpos.stop();
                bpos.join();
                // they will call remove on their own
            }
        }

        // Step 5. Update nameservices whose NN list has changed
        if (!toRefresh.isEmpty()) {
            LOG.info("Refreshing list of NNs for nameservices: " +
                    Joiner.on(",").useForNull("<default>").join(toRefresh));

            for (String nsToRefresh : toRefresh) {
                BPOfferService bpos = bpByNameserviceId.get(nsToRefresh);
                ArrayList<InetSocketAddress> addrs =
                        Lists.newArrayList(addrMap.get(nsToRefresh).values());
                bpos.refreshNNList(addrs);
            }
        }
    }

    /**
     * Extracted out for test purposes.
     */
    protected BPOfferService createBPOS(List<InetSocketAddress> nnAddrs) {
        return new BPOfferService(nnAddrs, dn);
    }
}
